Isomerization of saturated hydrocarbons



Dec. 1945. J. o. IVERSN ISOMRIZATION 0F SATURATED HYDROCARBONS Filed oct. 7, 1942 Patented Dec. 11, 19454 IsoMnaIzA'rIoN or sA'rUaA'rED maocamsous John 0. Iverson, Chicago, Ill., assignor to versal Oil Products Companyfchicago, corporation o! Delaware Unilll., a

Application October 7, 1942, Serial No. 461,13l

(Cl. 26o-683.5)

16 Claims.

This invention relates to the isomerization of saturated hydrocarbons and deals more specifically with the isomerization of saturated hydrocarbons wherein hydrogen is introduced into the reaction zone to prevent extensive decomposition of the hydrocarbons.

The isomerization of saturated hydrocarbons, particularly paranic hydrocarbons has become increasingly important in the past few years. In

this reaction the normal or mildly branched chain paraflins undergo a molecular rearrangement to form highly branched chain molecules. In general, these highly branched chain'molecules are considerably more reactive than their normal or less branched chain counterparts and are 'extensively used in the preparation of high antiknock motor fuels by the alkylation of the isoparafllns, particularly isobutane and isopentane with oleiinic hydrocarbons. 'Ihe isomerization reaction has also been utilized for the reforming of saturated hydrocarbon mixtures containing parat# iins and naphthenes such as straight run gasohnes and naphthas or fractions thereof to increase the antiknock value of these mixtures.

yThis reaction has generally been conducted using a combination catalyst comprising metallic halides of the Friedel-Crafts type promoted by hydrogen halides with the more frequent combi.

nation being aluminum chloride and hydrogen chloride. Other combinations such as the chlorides and bromides of zirconium, iron and zinc either alone or admixed with aluminum chloride and activated by hydrogen chloride or hydrogen bromide have also been used.

In the ordinary method ot operation considerable decomposition of the hydrocarbons is obtained as the result of numerous side reactions which occur simultaneously with the isomeriza tion reaction.

This decomposition not only materially decreases the egective yield of the process because oi the degradation of a portion of the charging stock, but has theadditional disadvantage in that it increases the catalyst consumption.

The fragmental hydrocarbons formed by the decomposition of the charging stock unite with the catalyst to form a hydrocarbon-catalyst cbmplex commonly termed sludgef Various .methods of operation have been used in an attempt to decrease or eliminate this sludge formation during the isomerization. A particularly eiective method is the introduction of hydrogen into the reaction zone which tends to hydrogenate the fragmental hydrocarbons and prevent their uniting with the catalyst. However, in the ordinary' chloride, maintaining tion products in Vsaid use of this operation considerable amounts of hydrogen are used which increases the cost of the operation materially. The present invention discloses an improved operation wherein the benecial eiects of the presence of hydrogen in the reactionA- zone arev obtained with a minimum amount of hydrogen being present, thereby substantially decreasing the cost -of the operation. The present invention also provides a simple method of separating the, hydrogen from the other materials so that it 'may be recyded t6 the reaction zone.

In one embodimenty thepresent invention relates to a process for the isomerization of an isomerizable saturated hydrocarbon which-comprises contacting said hydrocarbon with an aluminum chloride catalyst disposed Within a catalyst zone in the presence of hydrogen under conditions regulated to form an aluminum chloridehydrocarbon mixture.l containing an amount of aluminum chloride sufficient to eiect subsequent isomerization, maintaining a liquid level of the aluminum chloride hydrocarbon mixture within said catalyst zone, contacting a portion of said catalyst-hydrocarbon mixture within an absorption zone with a mixture of hydrogen chloride and hydrogen obtained as hereinafter set forth, withdrawing the hydrogen substantially free from hydrogen chloride from the absorption zone and introducing said hydrogen into the catalyst zone, introducing the hydrocarbon-aluminum chloride mixture containing absorbed hydrogen chloride into a reaction zone maintained under isomerizing conditions o! temperature and pressure in the presencey of hydrogen and hydrogen a liquid level of the reacreaction zone, withdrawing a portion of the liquid reaction products from said reaction zone, separating thel hydrogen and hydrogen chloride from said reaction products, recycling said separated hydrogen and hydrogen Achloride into said absorption zone as hereinbeore set forth, and separating the isomerized hydro carbons from the .unconverted hydrocarbons which may be recycled to the reaction zone.

The present invention is more clearly explained in the description of the accompanying drawing whichV diagrammatically illustrates in conventional side elevation one type of apparatus in which ,the objects of the present invention may be accomplished. For simplication, such Vunits as furnaces, pumps, heat exchangers, condensers, etc., which are non-essential to the explanation -have been eliminated from the drawing. For iurther simpliilcation, the drawing will be described relative to a pentane isomerization process. However, it should be understood that this simplification does not place vany undue limitation upon this invention since the apparatus described is adaptable to the isomerization of other saturated isomerizable hydrocarbons included within the broad scope of this invention.

Referring to the drawing, the normal pentane is introduced through line I and line 2 containing Although only one aluminum chloride tower is valve 3 into line 36. Alternatively, the normal 10 pentane may be introduced from line I through line 4 containing valve 5 into line 1 or from line I through valve 6 into line 25. The point of introduction of the normal pentane will be 'dependstock being used. If, for example, the charge co'ntains a considerable amount of isopentane, it will be introduced through line 86 containing valve 81 directly into fractionator 24 wherein the isoent primarily upon the character of the charging pentane is separated from the normal pentane. 20

On the other hand, if a considerable amount of unsaturated materials is present in the charging stock, the charge will be introduced through line containing valve 26 into aluminum chloride treater 21 where it is contacted with an aluminum 25 chloride-hydrocarbon solution formed as hereinafter set forth. The term unsaturates as used inv this specification and appended claims isintended to include both oleiinic and aromatic hydroshown in the drawing, more than one may be employed continuously or intermittently. Thus,

, while the pentane and hydrogen are being introduced through aluminum chloride tower l in order to introduce the catalyst into reactor I5, an-v other chamber similar to catalyst tower 9 may be emptied, cleaned and refilled with a, fresh charge of aluminum chloride so that the duplicate tower may be used in placeof tower 9 when it becomes necessary to clean and recharge the same.

The catalyst-hydrocarbon mixture containing hydrogen dissolved therein leaves chamber 9 i through line I0 and is directed through valve II is withdrawn through line 10 containing valve 1I v and commingled with the aluminum chloridecarbons. The unsaturated hydrocarbons react with the aluminum chloride to form aluminum chloride-hydrocarbon complexes which settle out of the hydrocarbonstream. These complexes are removed through line 82 containing valve 89 and may be recovered as a product ofthe reaction or may be recycled to reactor I5. The normal pentane charge along with unconverted normal pentane and higher boiling hydrocarbons formed as hereinafter set forth from fractionator 24 leave the aluminumchloride treater 21. through line 4 28 containing valve 29 and pass through the caustic wash chamber anwherein the remaining portions of aluminum chloride are removed by neutralization with the caustic. The caustic treated stream leaves chamber 30 through line 3| containing valve 32 and is introduced into fractionator 33 wherein the heavier hydrocarbons are separated from the normal pentane and withdrawn` through line 34 containing valve 35. These heavpentane solution from aluminum chloride tower 9. The aluminum chloride-pentane mixture containing hydrogen chloride and hydrogen dissolved therein, leaves absorber I2 through line I 3 containing valve I4 and is introduced into reactor Il wherein a substantial portion of the pentane is converted to isopentane, in the presence of hydrogen and hydrogen chloride being introduced into reactor I5 through line 50 containing valve 59.

It may be desirable under certain conditions of operation to limit the hydrogen being introduced into reactor I5 to the amount dissolved in the pentane aluminum chloride mixture. This may be accomplished by closing valve-59 and introducing the necessary hydrogen chloride through 5 line 84 containing valve'.

Reactor I 5 will be maintained under conditions such that extensive isomerization occurs without ier hydrocarbons are recovered as al product of the reaction. 'I'he normal pentane charge substantially free from unsaturated materials leaves fractionator 33 through line I6 and valve `I'I into line 1 and is directed through valve 8 into alumiexcessive decompositionV of the normal pentane. The temperature within reactor I5 will vary within the approximate range of 50 to 300 F. 'I'he hydrogen pressure within reactor II will vary `depending upon the temperature of the operation .but will be suillclent to maintain the pentane -fin ya. mixed or substantially liquid phase. The

num chloride tower 9 along with hydrogen intro- 55 duced as hereinafter set forth.' v

The liquid pentane passes down through a catalyst bed disposed in tower 9 and dissolves a sufiicient amount of aluminum chloride to promote isomerization in a subsequent reaction zone. Ihe 00 amount of catalyst dissolved in the pentane is dependent upon the temperature at which the catalyst tower is maintained which will be controlled by the catalyst concentration desired in the subsequent 'reaction zone. Ordinarily, the tempera- 6 ture will be within the range of to '300 F.

A pressure of hydrogen sufficient to maintain the pentane in a liquid-phase is maintained 'in the aluminum chloride tower 9. One of the features of the present invention is the maintenance of a 7 I drawn from the reaction none which must later liquid level of the aluminum chloride-pentane solution within catalyst zone 9 so that the amount g of hydrogen removed from 'said zone will be only that portion soluble in the pentane-catalyst mixture under the particular conditions of operation.

hydrogen chloride concentration will ordinarily be less than 40 mol percent of the pentane charge.

Reactor l5 may comprise a large vessel packed with materials such as quartz chips. granular silica-alumina composites, alumina, activated charcoal, crushed nre-brick, and other conventional packing materials or materials Drbvidin a large surface area such as spongy iron and other metals. Alternately, reactor I5 may be a large chamber having some means therein which will 5 `provide suilicient contact between the catalyst and hydrocarbon to lproduce the desired degree of isomerizatlon. One of the essential features of this invention is the maintenance of a. liquid level of reaction products in reactor Il. By operating in this manner the amount of hydrogen withwill be controlled by the temperature and pressure of the operation. l

from settler I8 through line I9 containing valve 2l and are directed into hydrogen-hydrogen chloride stripper 2l wherein the hydrogen and hydrogen chloride are separated from the isopentane, unconverted normal pentane and higher boiling hydrocarbons. Thehydrogen-hydrogen chloride mixturels withdrawn through line 52 containing valve 53 to'receiver 54 wherein any entrained liquid is separated therefrom The hydrogen-hydrgen chloride mixture substantially tree from any liquid hydrocarbons is withdrawn from receiver 54 through line 51 and is directed into either reactor I5 or hydrogen chloride absorber I2, as hereinbefore set forth. The entrained yliquid is withdrawn from receiver 54 through line 55 containing valve 5B and commingled with the hydrocarbon stream in line I9.

The isopentane, normal pentane and higher boiling hydrocarbon mixture, substantially free of hydrogen and hydrogen chloride is Withdrawn from stripper 2| through line 22 containing valve 23 and is directed into fractionator 24 wherein the isopentane i.; separated from the higher boiling hydrocarbons and unconverted pentane and with-t drawn through line 6I containing valve 62, condensed and recovered as a product of the reaction. The unconverted normal pentane and higher boiling hydrocarbons containing. small amounts of ing conditions in a reaction zone in the presence oi a metallic halide catalyst of the Friedel-Crafts type, a hydrogen halide and hydrogen, removing the resultant products from said zone and separating therefrom a gas containing hydrogen and hydrogen halide, simultaneously with the foregoing operation passing a saturated hydrocarbon liquid through a catalyst supply zone containing a metallic halide of the Friedel-Crafts type and therein dissolving at least a portion of the catalyst in said liquid, maintaining the lastnamed zone under hydrogen pressure whereby to dissolve hydrogen in the hydrogen-catalyst solution, removing a liquid solution comprising hydrocarbon liquid, dissolved catalyst, and only the amount of hydrogen soluble therein from the supply zone and contacting said gas therewitlito dissolve hydrogen halide inthe solution and to separate hydrogen from hydrogen halide, introducing thus separated hydrogen to the catalyst supply zone, and supplying the solution from the contacting step to said reaction zone,

. 2'. An isomerization process winch comprises subjecting a paramnic hydrocarbon to isomerizing conditions in a reaction zone in the presence of an aluminum halide, a hydrogen halide and hydrogen, removing the resultant products from saidzone and'separating therefrom a gas containing hydrogen and hydrogen halide, simultaneously with the foregoing operation passing a parafiinic liquid through a catalyst supply zone containing an aluminum halide and therein dissolving aluminum halide in said liquid, mainaluminum chloride dissolved therein are withdrawn.- through line 1 and recycled .to aluminum chloride tower 9. A portion of this stream may be directed into either lines I0 or I3 through lines 14 and 15 containing valves 15 and 11, respectively. To prevent a build-up of heavier hydrocarbons within the system, a portion is withdrawn through line 25 containing valve 26 and aluminum chloride treater 21 and is subsequently separated from the normal'pentane in iractionator 33, as hereinbefore set forth. The unconverted normalpentane along with the fresh charge is recycled ,to aluminum chloride tower 9 through line 36. A portion oi .this stream may be directed into lines I0 and I3 through lines 38 and 40 containing valves 39 and 4I respectively.

Since the isomerization reaction is an exothermic reaction, it is necessary to provide some method for maintaining a, substantially constant conversion temperature within reactor I5. This is accomplished by introducing a cool portion of the stream from line 36 into line 43 through valve 42 into the,y various quench lines, namely lines 44, 46 and 48 containing valves 45, 41 and 49 respectively. The hydrogen and hydrogen chloride necessary for starting the isomerization reaction and small amounts of make-up during the operation are introduced through line 59 containing valve 80 to line 51.

It is to. be understood that the above descrip,- tion is merely illustrative of the invention and is not to be construed as a limitation thereog except in so far as the same is defined in the appended claims.

I claim as my invention:

. l. An isomerization process which comprises taim'ng the last-named zone under hydrogen pressure whereby to dissolve hydrogen in the solution of aluminum halide in parailinic liquid, removing a liquid solution comprising parafnic \liquid, dissolved aluminum halide, and only the amount of hydrogen soluble therein from the 40 supply zone and contacting said gas therewith to dissolve hydrogen halide in the .solution and to separate hydrogen .from hydrogen halide, introducing thus separated hydrogen to the catalyst supply zone, and supplying the solution from the contacting step to said reaction zone.

3. An isomerization process which comprises subjecting a parailinic hydrocarbon to isomerizing conditions in a reaction zone in the presence of aluminum chloride, hydrogen chloride and hydrogen, removing the resultant products from said zone and separating therefrom a gas containing hydrogen and hydrogen chloride, simultaneously with the foregoing operation passing a paraihnic liquid through a catalyst supply zone containing aluminum chloride and therein forming a. solution of aluminum chloride in said liquid, maintaining the last-named zone under hydrogen pressure whereby to dissolve hydrogen insaid solution, removing a liquid solution containing only the amount of hydrogen soluble therein .from the supply zone and contacting said gas therewith to dissolve hydrogen chloride in the solution and to separate hydrogen from hydrogen chloride, introducing thus separated hydrogen to the catalyst supply zone, and supplying the solution fromthe contacting step to said reaction zone.

4. An isomerization process which comprises introducing a saturated hydrocarbon in substantially liquid phase into a catalyst supply zone containing a metal halide isomerizing catalyst of the Friedel-Crafts type and therein dissolving at least a portion Iof the catalyst in said hydrocarbon, maintaining said zone under hydrogen pressure, withdrawing from said zone a liquid hydrocarbon stream containing dissolved metal halide catalyst and only the amount of hydrogen soluble in said stream, subjecting said stream to isomerizing conditions to effect isomerization of said saturated hydrocarbon, separating hydrogen from the resultant reaction products, and introducing thus separated hydrogen to said catalyst supply zone.

5. The process of claim 4 further characterized Y in that the isomerization is carn'ed out in the presence of a hydrogen halide.

6. An isomerization process which comprises passing a saturated hydrocarbon in substantially liquid phase downwardly through a catalyst supply zone containing a metal halide isomerizing catalyst of the Friedel-Crafts type and therein dissolving at least a. portion of the catalyst in said hydrocarbon, introducing hydrogen into said catalyst supply zone and maintaining saidzone under hydrogen pressure, maintaining a liquid level in said catalyst supply zone during the passage of said hydrocarbon therethrough, withdrawing from a point below the liquid level in said catalyst supply zone a liquid hydrocarbon stream containing dissolved metal halide catalyst and dissolved hydrogen, introducing said stream and a hydrogen halide promoter into a reaction zone and therein eiectingisomerization of said saturated hydrocarbon, separating hydrogen and hydrogen halide from the resultant isomerization products, and returning thus separated hydrogen to said catalyst supply zone.

'1. An isomerization process which comprises passing a saturated hydrocarbon in substantially liquid phase downwardly through a catalyst supply zone containing a metal halide` isomerizing catalyst of the Friedel-Crafts type and therein 8. The process of claim 7 further characterized in that a mixture oi hydrogen and hydrogen halide is separated from the liquid stream withdrawn from said reaction zone, the liquid hydrocarbon stream withdrawn from said catalyst supply zone is contacted with said mixture to substantially completely absorb hydrogen halide therefrom, the resultant solution of hydrogen halide in said liquid hydrocarbon stream is supplied to said reaction zone, and the unabsorbe'd hydrogen substantially free of hydrogen halide is introduced into said catalyst supply zone.

9. 'I'he process of claim 6 further characterized in that,said 'metal halide comprises aluminum chloride and said hydrogen halide comprises hydrogen chloride.

10. The process of claim 7 further characterized in that said metal halide comprises aluminum chloride and said hydrogen halide comprises hydrogen chloride.

11. The process of claim 4 further characterized in that said saturated hydrocarbon comprises l ized in that the temperature in said catalyst supstream containing dissolved metal halide catalyst drogen halide promotor into said reaction zone and eiecting isomerization of said saturated hy,- `drocarbon therein, maintaining a liquid level in 'said reaction zone during the passage o'- the reply zone is within the range of 100 F. to 300 F.

14. 'I'he process of claim 6 further characterized in that said reaction zone contains a solid packing material. l

15. An isomerization process which comprises introducing a saturated hydrocarbon in substantially liquid phase into a catalyst supply zone con-'- taining a metal halide isomerizing catalyst o! the Friedel-Crafts type and therein dissolving at least a portion of the catalyst in said hydrocarbon. maintaining said zone under hydrogen pressure. withdrawingfrom said zone a liquid hydrocarbon and only the amount of hydrogen soluble in said stream, subjecting said stream to isomerizing conditions in a reaction zone to effect isomerization of said saturated hydrocarbon, maintaining a liquid level and a gaseous atmosphere of hydrogen in said reaction zone, withdrawing from said reaction zone a liquid hydrocarbon stream containing only the amount of hydrogen soluble in said stream, separating hydrogen from the resultant reaction products, and introducing thus separated hydrogen to said catalyst supply zone.

16. The process of claim 6 further characterized in that a liquid leveland a gaseous atmosphere of hydrogen are maintained in said reaction zone and a. liquid hydrocarbon stream containing dissolved hydrogen and hydrogen halide is withdrawn from said reaction zone.

JOHN o. IvnasoN. 

